Dutta Research

Research at the EERS Lab

1) Atomic materials for electrochemistry:

Atomic interface engineering using Mn-Nx-Cx structural unit with Mn-Nx moiety on carbonaceous materials can be a major strategy to regulate interfacial/bulk electrochemistry by inducing a local electric field. In this study, we aim to incorporate Mn-rich layers that enhance structural integrity while maintaining a low redox voltage,
which facilitates the incorporation of Mn-Nx atomic dispersion in multiwalled N-doped carbon nanofiber (NCNF). Our X-ray absorption spectroscopy (XAS) analysis and aberration-corrected angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) analysis support two types of Mn-Nx regions
with higher and lower atomic density on N-CNF. Incorporating Mn-N4 single atom modulates the local electrical field for fast bulk Na+ transportation to enhance intrinsic electrical conductivity with numerous additional reaction sites. Notably, the Mn-N4-N-CNF anode in the coin cell demonstrates an outstanding rate capability of 417
mAh g􀀀 1 at 20 mA g􀀀 1 and stable charge-discharge performance for current rates 20–2000 mA g-1 along with a long cycling stability test at 1000 mA g􀀀 1. Mn-N4-N-CNF cell retained 95 % of the highest capacity, nearly 100 % Columbic efficiency, and a 500-cycle life. This work provides an understanding of a multiwalled N-CNF multilayer
with incorporated Mn-N4 single atom, achieving a controllable defect and morphology engineering to offer an advanced anode material with faster Na+ charge transfer for SIBs. The GITT profile and the calculated diffusion coefficient suggest an improved diffusion of Na+ enabled by an effect of Mn-SA and N-CNF-multi-walled
structure.

Atmomic scale materials will be electronically tuned and further explored with multi-atomic medium and high entropy materials for their advanced electrochemical cell processes which includes paired electrolysis-based processes including enzyme mimicking, power density analysis, DFT simulations, molecular dynamic simulations (in collaboration with experts) and new electrochemical processes for charge storage and sensing.

2) Energybioscience and enzyme mimicking electrochemistry

Ni–N4–PAN–NC, consisting of an atomic Ni–N4 site, mimics the intramolecular electron-harnessing of natural laccase (LAC) confined in a zeolitic imidazolate framework-8 (LAC@ZIF-8) for anodic electrooxidation of bisphenol-A (BPA). We have introduced a facile π-conjugated unit of polyacrylonitrile (PAN)-resorcinol-derived N-doped conjugated -C≡N. The atomically dispersed Ni-single-atom in Ni–N4 - PAN–NC exhibits high activity for the paired electrolysis of ORR and the electrooxidation of BPA with an enhanced current density. The single Ni–N4–PAN–NC electrode effectively withdraws the electrons from electrooxidizing BPA due to a built-in electric field via incorporation of Ni–N4. The paired electrolysis of Ni–N4–PAN–NC biofuel cells is determined by LSV, EIS, and power-polarization curve for anodic electrooxidation of BPA. Machine learning molecular dynamics (ML-MD) simulation depicts non-covalent interaction (hydrogen bonding) between the O-hydroxyl of BPA and the N of the Ni–N4–PAN–NC, suggesting preferential adsorption on the Ni–N4–PAN–NC surface via weak van der Waals interactions and π–π stacking between the aromatic rings of BPA and the conjugated PAN-NC. An increased power density with increased concentration of BPA in the absence of ABTS suggests a DET mechanism of BPAelectrooxidation on Ni–N4, unlike a MET in the presence of ABTS when using LAC@ZIF-8. Thus, single atomic Ni − N4 opens avenues with a DET mechanism. Similarly, we have programmed a research strategy for mimicking several oxidereductase enzyme for constructing H-cell type biofuel cells along with design of new single-atom materials for active mimic of those enzymes. Gaining maximum power density from these processes are primary goals for a transformative development.

3) Sodium-ion and Zn-metal batteries

Sluggish diffusion kinetics of Na+ drastically restrain the rate capability and capacitance of the anode for sodium-ion batteries (SIBs). Herein,
a Fe single-atom strategy is employed to construct Fe─N4─O2 active sites closely coupled with Fe3C species, establishing strong electronic interactions
and, more importantly, an optimized coordination environment through precise tuning of their composition ratio with wood-derived nanoporous
carbon (WNC) support. The charging Na+ through nanoporous carbon of Fe─N4─O2–WNC anode is revealed by electrochemical capacitive and
charge–discharge studies to establish a reversible conversion and diffusion of Na+ supported by theoretical calculation of Na+ migration energy (eV)
against the diffusion path. Fe─N4─O2–WNC anode, assembled with sodium foil as counter electrodes in a coin cell, exhibits a significant discharge-specific
capacity of 318 mAh g−1 at a current density of 50 mAg−1. The electrochemical analysis support the role of Fe─N bonding in modulating the electronic
environment of Na+ diffusion sites. The incorporation of Fe─N4─O2 in WNC results in 1) faster Na+ diffusion through hollow (H) sites, 2) stretching
of the Fe─N bond during discharge cycles. In addition, Fe─N4─O2–WNC anode promises for the manufacturing of advanced SIBs from a renewable
material and thereby enhancing the investigation of sodiophilic Fe─N sites.

Reducing the reaction barriers of the oxygen reduction reaction (ORR) and accelerating the reaction kinetics of zinc-air batteries (ZABs) requires unique advantages in regulating electron orbitals with weakened adsorption of oxygen intermediates and conductive dissociation with a negative shift of the d-band centre. The sluggish ORR and unstable Zn/electrolyte interface at relatively high-rate ability require bifunctional electrolysis. Herein, a multi-walled carbon nanotube (MWCNT) and resorcinol-formaldehyde (RF) polymer composite resulted nanofiber in which Fe and Co-atomic sites were incorporated in FeA-CoA/MWCNT-NC.

4) Supercapacitor and capacitive deionization

Electrochemical supercapacitors and the electrochemical oxidation of biomass-derived oxygenates have great significance for long-term high-performance devices. However, appropriate sites with redox features remain a bottleneck for electrochemical oxidation and capacitance retention. Herein, N-doped
carbon sheets with Mn-phosphate-doping and Co-metal nanoparticles were synthesized via a facile one-pot activation and calcination of the layered potassium phthalimide salt without inclusion of any additional activators or template. The unique 2D-structure of the obtained microporous carbon flakes with a layered structure provides a sturdy N-C matrix for prolonged charging/discharging with abundant active adsorption sites and an effective route for rapid electrolyte ion transport with a shorter diffusion distance for the adsorption/desorption of ions. Through these merits, K-Ph-NC offers high capacitance and outstanding rate performance with an incredible energy density in capacitor devices, and the specific capacitance of the as-prepared K-Ph-NC is proportional to the number of micropores. K-Ph-NC was further transformed to a K-Ph-Oxide, a graphene oxide version of K-phthalimide, by using an improved Hummer's method by using Mn-salt and phosphoric acid, which resulted in a phthalimene oxide doped with Mn-phosphate. In addition, a composite of K-Ph-NC with ZIF-67 was thermally calcined at 700 °C under an Ar atmosphere, which resulted in e-ZIF-67/K-Ph-NC with an etched surface. A comparative electronic and structural analysis followed by a capacitance retention and electrochemical oxygen evolution reaction study revealed the role of Co-nanoparticles as compared to the Mn-phosphate doping in the resulting materials. A symmetric supercapacitor device exhibited a maximum SE value of 22.7 W h kg−1 with a maximum SP of 10 416.7 W kg−1, which is mainly due to the favorable microporous pore architecture in e-ZIF-67/K-Ph-NC as compared to K-Ph-NC and K-Ph-Oxide. This highlights the role of cobalt nanoparticles in e-ZIF-67/K-Ph-NC with an etched outer surface. A promising overpotential of 450 mV at 10 mA cm−2 in the OER by e-ZIF-67/K-Ph-NC can be correlated to the charge transfer resistance across the electrode–electrolyte interface.

5) Bioelectrode and biofuel cells

New enzyme and protein-based electrode will be designed for new electrochemical process. This includes enzyme and protein composites by preserving their activity for advanced electrochemistry.

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